以苯乙炔改質之矽奈米顆粒:合成及其特性

Abstract

本篇研究合成新穎苯乙炔-矽奈米顆粒，並分析其光學性質；藉由此新穎之官能基-苯乙炔的表面改質，製造可於溶液中良好分散且具有顯著、穩定光激發螢光性質(Photoluminescence)的矽奈米顆粒。為分析此矽核-官能基結構為Si -C=C-Ph之苯乙炔矽奈米顆粒的特性，我們同時合成結構極為相似，即矽核-官能基結構為-Si-C-C-Ph的苯乙烯-矽奈米顆粒，做為對照。相較於未改質的矽奈米顆粒，此兩種改質後之矽奈米顆粒皆有效地改善了其在溶液中的分散能力，並顯露光激發螢光性質。然而，苯乙炔-矽奈米顆粒的光激發螢光效率及穩定度皆遠優於苯乙烯-矽奈米顆粒(苯乙炔-矽奈米顆粒存放於大氣中18天之後仍維持其光激發光性質;苯乙烯-矽奈米顆粒之光激發光性質存放於大氣中12天即有明顯衰變)。此差異乃歸因於苯乙炔與苯乙烯之不同反應性：苯乙炔之乙炔基團的反應性優於苯乙烯之乙烯基團，使得苯乙炔之改質能達到更完全的表面包覆(較少表面缺陷)，而展現較佳的光激發螢光效率及穩定度。此外，我們觀察到，此兩種改質之矽奈米顆粒，由於其官能基本身光激發螢光性質及官能基-矽奈米核交互作用程度的差異，使得其產生光激發螢光之機制略有差異。藉由不同激發波長之光激發螢光光譜(PL spectra)及螢光激發光譜(PLE spectra)之分析，我們推斷此兩種改質之矽奈米顆粒之整體光激發螢光皆包含單獨之官能基和矽奈米核之光激發螢光特性，但苯乙炔-矽奈米顆粒另外顯現來自於官能基-矽奈米核交互作用之貢獻，而苯乙烯-矽奈米顆粒則無。此差異可歸因於苯乙炔-矽奈米顆粒之–Si-C=C-Ph鍵結，其共軛結構易與矽奈米核產生能量傳遞，因此呈現較顯著的官能基-矽奈米核交互作用，而苯乙烯-矽奈米顆粒與矽奈米核的鍵結(-Si-C-C-Ph)則無此類共軛結構。

Novel phenylacetylene-functionalized Si (PH-Si) nanoparticles were synthesized and their photoluminescence (PL) properties were analyzed, in order to achieve Si nanoparticles that were well-dispersed in solutions with strong and stable PL. Compared with styrene-functionalized Si nanoparticles (ST-Si), which contained –Si-C-C-Ph linkage instead of the –Si-C=C-Ph linkage of the PH-Si, the PH-Si nanoparticles had significantly higher PL efficiency, better PL stability over time stored in air (no change for 18 days vs. rapid degradation in 12 days), and stronger ligand-Si-interactions-induced PL characteristics, while both PH- and ST-Si nanoparticles showed greatly improved dispersion in solvents over non-functionalized Si nanoparticles. The stronger and more stable PL of the PH-Si was attributed to the greater reactivity of the acetylene moiety of phenylacetylene than the ethylene moiety of styrene, which achieved more complete passivation of the Si surface. Excitation-wavelength dependence of the PL spectra and the PLE spectra of the Si nanoparticles indicated that the PL of the PH-Si and S-Si nanoparticles were both combinations of the individual PL of the functional group and the Si core, but that the PL of the PH-Si nanoparticles contained significant contributions from functional-group-to-Si interactions while the PL of the S-Si nanoparticles did not. The significant functional-group-to-Si interactions of the PH-Si nanoparticles were attributed to the –Si-C=C-Ph linkage, which may enhance charge transfer between the PH group and the Si core through the conjugated structure; on the other hand, the S-Si linkage (-Si-C-C-Ph) were not conjugated and thus did not show such interactions.